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Old 9th April 2012, 05:25 AM   #11
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Quote:
Originally Posted by ruffrecords View Post
When you say 'output <2.7K ohm' do you mean the load it is driving is 2.7K ohm or you want the output impedance to be < 2.7K ohms?

Cheers

Ian
Output impedance is <2k7
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Old 9th April 2012, 06:00 AM   #12
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Hi all!
Is this the schematic can be developed valve line stage preamp with PCC88 or with ECC88 or some are needed changes ?
Here's the comment.
thank you and cheers!
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File Type: jpg Preamp with PCC88.JPG (157.1 KB, 149 views)

Last edited by formula 22; 9th April 2012 at 06:13 AM.
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Old 9th April 2012, 06:18 AM   #13
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apart from being more expencive, 6H30 ?
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Old 9th April 2012, 06:53 AM   #14
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Either schematic should like this look!?
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Last edited by formula 22; 9th April 2012 at 07:13 AM.
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Old 9th April 2012, 07:21 AM   #15
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ehh, is out connected correctly ?
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Old 9th April 2012, 07:26 AM   #16
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Originally Posted by tinitus View Post
ehh, is out connected correctly ?
If the wrong out, please give the proposal.
thank you
P.S.
The output is this of to reduce the gain to 10x

Last edited by formula 22; 9th April 2012 at 07:30 AM.
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Old 9th April 2012, 07:42 AM   #17
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Quote:
Originally Posted by formula 22 View Post
If the wrong out, please give the proposal.
thank you
Im not that clever, sorry
I just thought it looked 'different'
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Old 9th April 2012, 01:54 PM   #18
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That schematic looks about right to me. Operating point is around 9mA, plate dissipation is under 1 watt. Gain should be close to 10 with that plate load pot divider. Output impedance may be higher than you desire because cathode bias resistor is not bypassed. This increases effective plate resistance from around 3K to about 10K and increases distortion.I would recommend bypassing the cathode resistor.

Cheers

Ian
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Old 10th April 2012, 05:57 AM   #19
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Quote:
Originally Posted by ruffrecords View Post
That schematic looks about right to me. Operating point is around 9mA, plate dissipation is under 1 watt. Gain should be close to 10 with that plate load pot divider. Output impedance may be higher than you desire because cathode bias resistor is not bypassed. This increases effective plate resistance from around 3K to about 10K and increases distortion.I would recommend bypassing the cathode resistor.

Cheers

Ian
Hi ruffrecords!
The signs of these changes on the cathode you think. Cathode to bypassing the resistor R1 = 220Ohm/0,25W and the electrolytic capacitor C1= 680uF/16V. I think that the anode current is about 11mA?.
This schematic now has as much gain and what is the output Impedance?
What is the gain without the capacitor C1?
Thanks and cheers!
P.S.
If you have another suggestion you name it.
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File Type: jpg Preamp with PCC88 (schematic-2).jpg (239.7 KB, 97 views)

Last edited by formula 22; 10th April 2012 at 06:18 AM.
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Old 10th April 2012, 06:24 AM   #20
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may I ask, why 1Mohm input impedance ?
usually only for musical instruments ?
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